Puerto Rico and the U.S. Virgin Islands are bracing for the howling winds and rain of Hurricane Maria after it smashed into the eastern Caribbean, with forecasters warning that "sustained hurricane-force winds should start on St. Croix soon."

Maria blew into the region with 260 km/h sustained winds and appears to be heading for islands already reeling in Irma's wake. Officials on Guadeloupe said a person was killed by a falling tree branch.

The U.S. National Hurricane Center said Tuesday night that the eye of the Category 5 hurricane was getting closer to St. Croix and the U.S. Virgin Islands, with maximum sustained winds of 280 km/h.

If the storm stays on its current track, the forecasters said, it will hit Puerto Rico on Wednesday, and then pass "just north" of the Dominican Republic late Wednesday and into Thursday.

Workers remove fallen tree branches from a road in Guadeloupe, where at least one death linked to the storm was reported. (Andres Martinez Casares/Reuters)

"Preparations against life-threatening storm surge and rainfall flooding and destructive winds should be rushed to completion," the centre said.

Puerto Rico Gov. Ricardo Rossello told CBC News Network on Tuesday that the island, which had been working to recover from Irma, is frantically preparing once again.

The governor said the main push right now is to get people into safe shelters.

"We know there's going to be a lot of damage," he said. "It's going to be catastrophic."

'We will need help'

The storm plowed into Dominica, a mountainous country of 72,000 people, late on Monday. Prime Minister Roosevelt Skerrit said on his Facebook page that "initial reports are of widespread devastation" and said he feared there would be deaths due to rain-fed landslides.

Dominica is particularly vulnerable to flooding because of its steep mountains, cut through with rivers that rage after a heavy rain.

"So far, the winds have swept away the roofs of almost every person I have spoken to or otherwise made contact with," Skerrit wrote. "The roof to my own official residence was among the first to go."

Hurricane Maria slams into Leeward Islands1:34

And he appealed for international aid: "We will need help, my friend, we will need help of all kinds."​

An official from the Caribbean island of Dominica said Tuesday afternoon that officials have been told that Maria tore the roofs off 70 per cent of the island's homes and that there have been unconfirmed reports of deaths.

Skerrit earlier described the fury of Maria as it made landfall.

"The winds are merciless! We shall survive by the grace of God," Skerrit wrote at the start of a series of increasingly harrowing posts on Facebook.

A half-hour later, he said: "My roof is gone. I am at the complete mercy of the hurricane. House is flooding." Seven minutes later, he posted that he had been rescued.

Eric Maire, the prefect, or highest French official, of Guadeloupe, said in a video via Twitter that some roads and homes were flooded and heavy rain is expected to continue. He told island residents to "remain inside" amid the flood threat and warnings by forecasters of possible landslides.

Rossello said Puerto Rico had 500 shelters capable of taking in up to 133,000 people in a worst-case scenario. Officials are particularly concerned about people in vulnerable homes that could suffer massive damage in a powerful storm.

He also said the Federal Emergency Management Agency was ready to bring drinking water and help restore power immediately after the storm, which could hit as a Category 5 hurricane.

"It's a storm unlike what we've ever seen here in Puerto Rico," he said.